Relay control system



Nov. 9, 1948. J. H. TEDDER RELAY CONTROL SYS'IBI Filed Oct. :5, 1945 FIG. 1.

FIG. 3;

77M: cozvmcrs 78 Patented Nov. 9, 1948 RELAY CONTBQL SYSTEM Joel H. Tedder, Los Angeles, Calif., asslgnor to International Business Machines Corporation, New York, N. Y., a corporation of New York Application October 3, 1945, Serial No. 620,079

1 Claim. 1

This invention relates to a relay circuit arrangement, such as utilized in the apparatus disclosed in an application of R. I. Roth et 9.1.. Berial No. 585,996. filed March 31, 1945.

This relay circuit arrangement is designed to provide a quick pick up and "drop out of a relay. The relay is of the type in which two windings are on a common core and act on a common armature to control relay contacts. One of the windingsis called the pick-up winding and the other is called the hold winding. When the armature is in fully retracted position, the hold Winding, as constructed and with the given current supplied thereto, is incapable upon its energization of moving the armature to its attracted position. But when the armature has been moved to its attracted position, narrowing the gap between the armature and hold winding, the energized hold winding is eifective to hold it there. The pick-up winding is utilized to eifect the movement of the armature from its fully retracted position to a position in which it is in the range of influence of the hold winding. After the pick-up winding has performed its function of moving the armature into the range of the hold winding, it may be deefnergized. For this purpose, current is supplied to the pick-up winding by way of a condenser. When the condenser has been charged, it interrupts current flow through the pick-up winding.

The circuits of the pick-up and hold windings are established upon the closure of an automatically operated switch. This switch, as shown, is a cam-operated switch, but it may be a relay switch or the like. Such switches are comprised of leaf spring blades, each provided with a contact stud. Owing to the resiliency of the blades, they rebound as a result of the force of engagement of the contact studs. When the rebound momentum of the blades has been dissipated, they spring together again. Rebound and engagement will occur repeatedly in progressively diminishin periods of oscillation until the contacts finally settle down to a sustained closed status. As a result of the intermittent closure and opening of the control contacts and in the absence of means involved in the present invention, short surges of current through the condenser which is in series with the relay pick-up winding may be produced, each insufflcient to product efiective energization of the pick-up winding, but the total effect of which would be to charge the condenser, preventing the flow of an effective energizing current for the pick-up winding even after the control contacts have settled down to a sustained closed status. By eifective energization of the pick-up winding" is meant a sufficient energization thereof to cause movement of the armature into the attracted position.

An object of the invention is to avoid this ditllculty by withholding control of the condenser over the relay until the winding has been effec- 'tively energized, whereby eflective energization of the pick-up winding is insured in spite of flutter of the circuit closing, control contacts.

More specifically, an object of the invention is to delay control by the condenser of current flow through the relay winding until the winding has first been eilectively energized and only then to place the condenser automatically in control of the current flow through the winding, whereby effective energization of the winding is insured despite flutter of the circuit closing contacts and deenergization of the winding is then eflected under control of the condenser.

It may be stated that an object of the invention is to provide an energizing circuit for an energizable element, such as an electromagnetic winding element, supplemented by a condensercharging, deenergizing circuit for the element, the energizing and'deenergizing circuits to be successively operative.

Other objects Of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of examples, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

In the drawings:

Fig. 1 shows the novel circuit arrangement.

Fig. 2 is a mechanical view of the control contacts and their operating cam.

Fig. 3 is a graph illustrating. the actions of the circuit arrangement with and without the condenser by-passing. means.

Referring to Fig. 2, the control contacts are designated 18. The contacts are provided on the resilient blades I1 and 19. These blades are tensioned in such manner that the contacts 18 normally remain open. To close the contacts 18, a cam l5 and its follower 1.8 are provided. The follower 18 is essentially a leaf spring, the back of which is engaged with a piece of insulation attached to the contact blade 11. When the follower I6 is on a low portion of the cam 15, the contacts 18 are allowed to stay open. Upon the turning of the cam 15 in counterclockwise direction, a higher portion or the cam moves into engagement with follower 7B, actuating the follower to the right. The follower, in turn, acts through the inand so on until they ultimately stay closed. It

may be noted that the rebounding action is promoted by the high speed at which the cam It is turned,

Referring to Fig. l, the circuit diagram, N des ignates the duo-wound relay. 'iihe hold winding is identified by the letter H while the pick-up winding is identified by the letter F. Both coils act on a common armature ARM. The circuit :ior coil ii extends from the positive side of a no v. D. C. source, through the coil iii, the contacts it, upon their closure, and certain contacts Aililh which may be assumed to be in closed status, to

ground. One circuit for coil P extends from the +1.10 V. D. C. sicle, through a condenser C8, the coil P, and via contacts :18 and neon, to ground. A parallel circuit for coil 1? extends from the +110 v. D. C. side, via normally closed relay contacts Nb, through coil P, and contacts it and A231), to ground. it is to he noted that when the relay contacts Nh are in closed condition, they shunt out the condenser C8.

Coils P and H have an equal number of turns, wound in the same direction about a common core. The coil H is composed of o. much finer wire than the coil P and has a considerably greater resistance. in practice, it has been found suitable to maize the resistance of coil 2H about twenty times that of coil 1?. Accordingly, upon the closure of contacts to, a current oi considerably higher value flows through the coil P than through the coil H. The flux generated by cell H is too small to shift the armature ARM from. its retracted to its attracted osition. But the flux generated by the coil P is considerably greater and adequate to bring the armature to its attracted position in which it may then be retained by the energized coil H even after cell P has been deenergized. The high current flow through coil P, if sustained continuously, would overheat the coil and possibly burn it out. Furthermore, after coil P has been effectively energized and has brought the armature into the range of in fluence or" the coil H. it is no longer necessary to maintain the coil P energized. For these reasons, it is desired to interrupt current flow through coil P after it has been energized and has performed its function of bringing the armature under the influence of coil l'l'.

With the contacts Nb closed, the full poten tial of about 110 v. D. C. will be applied to the coil P and maximum current will flow through the coil while contacts l8 are in closed condition. When coil P has been effectively energized and shifted the armature to attracted position, the

armature-operated relay contacts Nb are opened. Thereupon, the current flow through coil P is by way of the condenser C8. A value for this condenser is chosen in accordance with the desired rate of decay of the coil P flux. As the tacts operated thereby. At the same time, the more sluggish coil H is eilective, by the time the armature has been shifted to attracted position by the coil P, to retain the armature in this shifted position.

As may now be understood. the relay contacts Nb serve to by-pass the condenser C8 until the coil P has been effectively energized. Thereupon.

contacts Nb open, whereupon the condenser charging circuit becomes operative to bring about the deenergization of coil P. The contacts Nb insure effective energization of coil P in spite of the flutter of contacts 18. To understand this better, the operation of the circuit were contacts Nb omitted will be contrasted with the operation of the circuit when contacts Nb are included.

Referring now to Fig. 3, the graph has, as one of its coordinates, opening and closing times of contacts we and, as its other coordinate, current flow through the coil N0?) The heavy portions of the horizontal coordinate represent closed intervals and. the light portions represent open intervals of contacts "iii, and it is assumed that a closure of the contacts first occurs at the time condenser charges. up, the current flow decays exponentially, substantially terminating when the condenser is fully charged. Accordingly, the coil P gradually ls deenergized. The condenser thus serves to limit the duration of high current flow in coil P and the duration of its energization.

The above circuit arrangement provides for rapid energization of coil P with a resulting rapid shifting of the armature and the relay coilrepresented by the intersection of the coordinates. Two open periods are indicated in Fig. 3 for the purposes of the explanation, but in practice, more than two open periods may occur. The solid portion of curve A and curves B and Bi roughly represent current how, by way of the condenser, through the coil IMP) if the by-passing contacts Nb (Fig. l) are omitted. The lines marked Wt, W2, W8 and we represent current flow when the contacts Nb-are included. As-

suming contacts Nb were omitted and that the contacts it did not rebound but remained continuously closed from the beginning, the current new in the charging circuit would be as roughly indicated by the combined solid and broken portions of curve A, and coil N(P) would. be effectively energized approximately at the point marked Ae. But the contacts l8 do rebound and open before point Ae condition is attained, so that the first surge of current through coil P would be as represented by the solid portion of curve A. The condenser would be partially charged but coil P would not be efiectiveiy energized. .During the momentarily open period of the contacts 1B,,con-

denser 08 would tend to discharge through the local circuit extending from one side of the condenser through coil P, thence through coil H, and back to the other side of the condenser. But the time constant of this circuit is so much greater than the momentarily open interval of the contacts l8 that the small discharge of the condenser during such momentary open interval may be safely ignored. Still assuming the absence of contacts Nb, during the second closed interval of contacts 18, current flow roughly represented by curve B flows in the charging circuit, further charging the condenser but not being of sufflcient mean value and duration to produce an effective energization of coil P. During the third sustained closed interval of contacts I8, the current flow would be as roughly represented by condenser, the current flow in the coil N(P), is at the peak during the first and second closed intervals of contacts 18 but the durations of such current flow as indicated by lines WI and W2 are too short to allow for effective energlzation of the coil P. During the third closed interval of contacts 18, peak current flows through coil P for a sufficient time, as indicated by line W3, to cause effective energization of the coil at approximately the point We. With the coil P now effectively energized, contacts Nb open, bringing the condenser into circuit. The condenser now charges, causing the current flow through coil P progressively to decrease, as roughly indicated by curve W4. Before the condenser has been fully charged, the coil P will have been deenergized.

As now understood. the invention provides an energizing circuit, including contacts Nb, for excluding'the condenser from control over the coil P until after the coil has been effectively energized. Thereupon, according to the invention, the coil P excludes the energizing circuit and renders eflective its own deenergizing, condenser charging circuit. Thus, as shown in Fig; 3, the condenser C8 has a capacity providing a time constant for the circuit through the condenser C8, coil P and contacts 18 permitting current flow through coil P to maintain it effectively energized for a predetermined substantial interval after the contacts Nb are opened but only for v that interval.

The coil P, when effectively energized, has brought the armature ARM into the range of influence of coil H. Coil H is continuously ener-ized as long as contacts 18 are steadily closed and is effective to maintain the armature in its attracted position. Upon sustained opening of contacts 18, the circuit of coil H is broken. Deenergization of coil H thereupon begins and is accelerated by the discharge of the condenser C8. The condenser discharging current is through coil P in one direction and through coil H in the opposite direction. Since the coils are wound in the same direction about a common core while the concurrent current flow through the two windings is in opposite directions, the fluxes produced by the windings oppose each other. Hence, deenergization of the coil H and the dropping or armature ARM are accelerated by the discharge of the condenser occurring upon sustained opening of contacts 18.

For convenience, contacts 18 may be referred to in the claims as a circuit closing switch. I

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form 6 and details of the device illustrated and in its operation may be made by those skilled in the art, without departingfrom the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claim.

What is claimed is:

A circuit arrangement comprising a relay having a pick-up and a hold winding wound in the same direction about a common core with the hold winding having a considerably greater resistance than the pick-up winding, an armature having a normal unattracted position from which it is moved to an attracted position only upon efiective energization of the pick-up winding said hold winding being effective while energized and after the armature is moved to its attracted position to hold the armature in said attracted position. and normally closed contacts controlled by the armature and opened upon movement of the armature from said unattracted position; a circuit closing switch of the resilient type tending to fiutter between .closed' and open status from the time of its initial closure until its settling down to a steady closed status; said pick-up winding, contacts and switch being connected in series across a source of voltage. and said hold winding being connected in parallel with the series-connected pick-up winding and contacts, whereby upon closure of, said switch for a sumciently prolonged interval the pick-up winding is effectively energized to move the armature and open the contacts and the hold winding is energized to hold the armature in its attracted position with the contacts open; and a condenser connected in shunt across said contacts, said condenser having a capacity permitting current flow through the pick-up winding to maintain it effectively energized for a predetermined substantial interval after the contacts are opened, but only for said predetermined interval, and accelerating appreciably the deenergization of the hold winding upon opening of said switch.

' JOEL H. TEDDER.

REFERENCES CITED The following referencesfare of record in the die of this patent:

UNITED srarns PATENTS 2,344,178 Sparrow Mar'.14. 1844 

